net.sf.saxon.expr

## Interface Negatable

- All Known Implementing Classes:
    AndExpression, BooleanExpression, BooleanFn, Empty, Exists, NotFn, OrExpression, ValueComparison

      public interface Negatable

  This interface is implemented by expressions that returns a boolean value, and returns an expression whose result is the negated boolean value

- - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `boolean` | `isNegatable(ExpressionVisitor visitor)` Check whether this specific instance of the expression is negatable
    `Expression` | `negate()` Create an expression that returns the negation of this expression

- - ### Method Detail

    - #### isNegatable

          boolean isNegatable(ExpressionVisitor visitor)

      Check whether this specific instance of the expression is negatable
      Returns:
        true if it is

    - #### negate

          Expression negate()

      Create an expression that returns the negation of this expression
      Returns:
        the negated expression
      Throws:
        `IllegalOperationException` - if isNegatable() returns false

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